Add v1.5 to travis build

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index a4d6cc5..9a3c1a8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,4 +5,5 @@
   - 1.2
   - 1.3
   - 1.4
+  - 1.5
   - tip